Apparatus for monitoring electron density and electron temperature of  plasma and method thereof

ABSTRACT

The present invention relates to an apparatus and method for monitoring an electron density and electron temperature of a plasma. The apparatus includes an electromagnetic wave generator that continuously transmits electromagnetic wave of a series of frequency bands, an electromagnetic wave transceiver connected to a plasma within a reaction container and electrically connected to the electromagnetic wave generator so that a frequency of the transmitted electromagnetic wave is correlated to the electron density and electron temperature of the plasma, the electromagnetic wave transceiver transmitting the electromagnetic wave, a frequency analyzer electrically connected to the electromagnetic wave transceiver, for analyzing the frequency of the electromagnetic wave received from the electromagnetic wave transceivers and a computer electrically connected to the electromagnetic wave generator and the frequency analyzer, for calculating a correlation between the electron density and electron temperature, and a corresponding electromagnetic wave based on a frequency band-based transmission command of the electromagnetic wave and the analyzed data.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, in general, to a technique that measuresand monitors an electron density and an electron temperature of a plasmaby probing and scanning each eigenfrequency, which is correlated to anelectron density and electron temperature of a plasma, in order tomonitor a process status using the plasma, such as a semiconductorfabrication process. More particularly, the present invention relates toan apparatus for monitoring an electron density and electron temperatureof a plasma, including a probe of an antenna structure fortransmitting/receiving a series of electromagnetic waves of a bandto/from a corresponding plasma and an analysis tool for analyzing thebands of specific electromagnetic wave cutoff frequency and absorptionfrequency of electromagnetic waves transmitted, which are cut off orabsorbed with respect to a corresponding plasma, and calculating anelectron density and electron temperature of the corresponding plasmabased on the analysis result, and a method thereof.

2. Background of the Related Art

In general, in the semiconductor fabrication process, plasma has beenwidely used due to the necessity of the miniaturization and lowtemperature of the process. Equipments used to fabricate semiconductordevices include an ion implantation equipment for implanting a desiredimpurity into a predetermined region of a wafer, a furnace for growing athermal oxide layer, a deposition equipment for depositing a conductionlayer or an insulating layer on the wafer, exposure and etch equipmentsfor patterning the deposited conduction layer or the depositedinsulating layer in a desired form, and the like.

Of the equipments, a plasma equipment for forming plasma within a sealedchamber of a vacuum state and implanting a reaction gas to deposit oretch a material layer has been widely used as the equipment fordepositing a predetermined material layer on the wafer or etching apredetermined material layer formed in the wafer.

This is because if a material layer is deposited using plasma, a processcan be performed at low temperature, such as that impurities within animpurity region formed in the wafer no longer diffuse, and theregularity in the thickness of the material layer formed in a waferhaving a large diameter is good.

In a similar way, this is because if a predetermined material layerformed on the wafer is etched using plasma, the etch regularity is goodover the entire waver.

In the plasma apparatus, tools capable of measuring an electron densityand an ion density within plasma include Langmuir probe, a plasmaoscillation probe, a plasma absorption probe, an OES (Optical EmissionSpectroscopy), a laser Thomson scattering method, and so on.

The Langmuir probe of the tools is widely used. In the conventionalLangmuir probe, in order to measure the plasma characteristic, the probeis inserted into plasma within a plasma chamber from the outside, andvoltages are varied from a negative potential to a positive potential(i.e., in the range of −200V to 200V) and are measured by varying anexternally supplied DC.

At this time, if a negative voltage is applied to the end of the probe,positive ions within the plasma are absorbed by the probe and a currentis therefore generated due to the ions. If a positive voltage is appliedto the end of the probe, electrons within the plasma are absorbed by theprobe and a current is therefore generated due to the electrons. In thiscase, the concentration of the plasma can be measured by measuring thegenerated current in order to analyze the correlation between thegenerated current and the voltage applied to the probe.

In the conventional Langmuir probe, the plasma density can be measuredin real-time while the process is performed because the plasma densityis measured by inserting the probe into the chamber. However, theconventional Langmuir probe has a noise problem due to RF (RadioFrequency) oscillation, a problem in that a thin film material isdeposited on the probe at the time of depositing the material in thesemiconductor process, a problem in that the probe becomes small due toetching at the time of a dry etch process, and the like. This makes itimpossible to apply the Langmuir probe to an actual mass-productionprocess.

Furthermore, the conventional plasma oscillation probe is constructed touse an electron beam and employs a hot filament in order to produce theelectron beam. However, the plasma oscillation probe is problematic inthat it has a narrow operating condition, such as that corresponding hotfilament is broken at a pressure of 50 mT or more. The plasmaoscillation probe is also problematic in that the reaction container ispolluted due to the evaporation of hot filament upon heating in order toemit thermal electrons.

Furthermore, the conventional plasma absorption probe is problematic inthat correction must be carried out using an accurate plasma densitydiagnosis tool before operation. A structure for improving the problemhas been proposed. However, the proposed structure requires severalsteps of complicate calculation processes for calculating an absolutevalue of a measurement density. In this case, the proposed structure isproblematic in that the effectiveness is low since physically assumedconditions are included.

In addition, the electron temperature measurement method employing OESis problematic in that it is commercially applied since sufficient dataare not accumulated.

Finally, the laser Thomson scattering method is problematic in that itis used only within a laboratory other than a mass-production systembecause the size is very large and the structure is very complicate.

Therefore, there is an urgent need for technology of a device structure,which can overcome the conventional problems, can measure an electrondensity and electron temperature of a plasma more rapidly andaccurately, can monitor a process thereof in real-time, and can beapplied to the mass-production system with less limitations.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made in view of the aboveproblems occurring in the prior art, and it is a first object of thepresent invention to provide an apparatus for monitoring an electrondensity and electron temperature of a plasma, including anelectromagnetic wave transceiver of an antenna structure, which cantransmit/receive electromagnetic waves of a series of bands so that afrequency band that is correlated to an electron density and electrontemperature can be measured/monitored in real-time.

It is a second object of the present invention to provide an apparatusfor monitoring an electron density and electron temperature of a plasma,including a frequency analyzer for analyzing a cutoff frequency and anabsorption frequency that are correlated to a corresponding electrondensity and electron temperature based on a frequency band of receivedelectromagnetic wave.

It is a third object of the present invention to provide an apparatusfor monitoring an electron density and electron temperature of a plasma,including a conveyer for conveying an electromagnetic wave transceiverwithin a reaction container such that spatial distributions can bemeasured by measuring the electron density and electron temperature ofthe plasma on a position basis within a plasma reaction container.

To achieve the above objects, according to an aspect of the presentinvention, there is provided an apparatus for monitoring an electrondensity and electron temperature of a plasma, including anelectromagnetic wave generator that continuously transmitselectromagnetic wave of a series of frequency bands, an electromagneticwave transceiver connected to a plasma within a reaction container andelectrically connected to the electromagnetic wave generator so that afrequency of the transmitted electromagnetic wave is correlated to theelectron density and electron temperature of the plasma, theelectromagnetic wave transceiver transmitting the electromagnetic wave,a frequency analyzer electrically connected to the electromagnetic wavetransceiver, for analyzing the frequency of the electromagnetic wavereceived from the electromagnetic wave transceiver, and a computerelectrically connected to the electromagnetic wave generator and thefrequency analyzer, for calculating a correlation between the electrondensity and electron temperature, and a corresponding electromagneticwave based on a frequency band-based transmission command of theelectromagnetic wave and the analyzed data.

The electromagnetic wave transceiver may include first and secondcoaxial cables that are electrically connected to the electromagneticwave generator and the frequency analyzer, respectively, and aredisposed in parallel, and a transmit antenna and a receive antenna thatare connected to and projected from one ends of the first and secondcoaxial cables, respectively, on the same axial line and are connectedto the plasma in order to transmit and receive the electromagnetic wave.

Each of the first and second coaxial cables may include adielectric-coated layer coated/shielded at a predetermined thickness.

Furthermore, the apparatus may further include a conveyer connected tothe other end of the electromagnetic wave transceiver, for causing theelectromagnetic wave transceiver to be selectively conveyed within thereaction container.

The conveyer may be driven by a stepping motor.

Alternatively, the conveyer may be driven by an oil-pressure cylinder.

It is preferred that the electromagnetic wave transceiver is disposedalong a radial direction of the reaction container in obtainingcharacteristic distributions of the plasma within the reactioncontainer.

Further objects, specific merits and novel characteristics of theinvention will become more apparent from the following detaileddescription and exemplary embodiments taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects and advantages of the invention can be more fullyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 shows the construction of an apparatus for monitoring an electrondensity and electron temperature of a plasma according to an embodimentof the present invention;

FIG. 2 is a cross-sectional view of transmit/receive antennas shown inFIG. 1;

FIG. 3 is a view illustrating convey within a reaction container of anelectromagnetic wave transceiver shown in FIG. 1;

FIG. 4 a is a graph illustrating cutoff frequencies measured using themonitoring apparatus according to an embodiment of the presentinvention;

FIG. 4 b is a graph illustrating absorption frequencies measured usingthe monitoring apparatus according to an embodiment of the presentinvention;

FIG. 5 is a graph illustrating electron density and electron temperaturemeasured using the monitoring apparatus according to an embodiment ofthe present invention; and

FIG. 6 is a flowchart illustrating a method of measuring an electrontemperature of a plasma according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An apparatus for monitoring an electron density and electron temperatureof a plasma according to an embodiment of the present invention will nowbe described in detail with reference to the accompanying drawings.

FIG. 1 shows the construction of an apparatus for monitoring an electrondensity and electron temperature of a plasma according to an embodimentof the present invention. FIG. 2 is a cross-sectional view oftransmit/receive antennas shown in FIG. 1.

Referring to FIGS. 1 and 2, the monitoring apparatus according to thepresent invention is adapted to measure a corresponding characteristicvalue and monitor the characteristic value in real-time, by finding acorrelation between the characteristics of electromagnetic wave and aplasma 100 a (more particularly, an electron density, an electrontemperature, and so on) and monitoring.

In order to have the correlation, the monitoring apparatus of thepresent invention includes an electromagnetic wave transceiver 200 fortransmitting/receiving electromagnetic wave to/from the plasma 100 a.For the purpose of such transmission/reception, the electromagnetic wavetransceiver 200 has an antenna structure.

What is contained in a cylindrical reaction container 100 is the plasma100 a. It has been known that if electromagnetic wave of a specific bandis transmitted to the plasma 100 a, corresponding electromagnetic waveis cut off or absorbed. A specific electromagnetic wave of a frequencyband that is cut off or absorbed as described above becomes the index ofan electron density or an electron temperature of the plasma 100 a. Itis therefore possible to obtain an electron density and electrontemperature of the plasma 100 a based on a correlation between theelectromagnetic wave and the plasma 100 a.

The correlation is established in the electromagnetic wave transceiver200. An electromagnetic wave generator 300 and the frequency analyzer400 are electrically connected to the electromagnetic wave transceiver200 in order to transmit electromagnetic wave to the electromagneticwave transceiver 200 or to analyze received electromagnetic wave.

In this case, the electromagnetic wave transceiver 200 includes twocoaxial cables 210, 220 that are disposed in parallel. Each of thecoaxial cables 210, 220 is surrounded with an additionaldielectric-coated layer 230 and a ground shield, for preventing thecoaxial cables 210, 220 from noise, heat, etc. Accordingly,electromagnetic wave can be transmitted and received more accurately.The dielectric-coated layer 230 may be formed of alumina or quartz.

Furthermore, transmit/receive antennas 210 a, 220 b are connected to andprojected from one ends of the coaxial cables 210, 220, respectively, onthe same axial line, and transmit/receive electromagnetic wave to/fromthe plasma 100 a.

Referring to FIG. 2, if the metal antennas 210 a, 220 a having a radius“b” are inserted into the plasma, a sheath 240 having a thickness “s” isformed on an outer surface of the antenna, thus surrounding thecircumference of the antenna. In the present embodiment, the antennas210 a, 220 a may be disposed at a distance of about 1 mm to 5 mm and mayhave a length of about 5 mm to 10 mm. The distance is only illustrative.The smaller the distance, the better. In addition, the length of each ofthe antennas 210 a, 220 a may be varied depending on a wavelength ofelectromagnetic wave used.

The electromagnetic wave generator 300 is connected to the other end ofthe first coaxial cable 210 and consecutively transmits electromagneticwaves of a frequency band of about 50 kHz to 10 GHz to the first coaxialcable 210 and the transmit antenna 210 a. Consequently, a series ofelectromagnetic waves of a frequency band can be transmitted to theplasma 100 a consecutively.

In this case, the cutoff frequency of the transmitted electromagneticwaves is cut off with respect to the plasma 100 a. The cutoff frequencycan be used to calculate and obtain an electron density of acorresponding plasma 100 a. Furthermore, an electromagnetic wave of aband absorbed by the plasma 100 a is an absorption electromagnetic wave,which can be used to calculate and obtain an electron temperature of acorresponding plasma 100 a.

The frequency analyzer 400 is also connected to the other end of thesecond coaxial cable 220. The frequency analyzer 400 serves to analyzean amplitude from a frequency of electromagnetic wave, which is receivedand obtained by the receive antenna 220 a and the second coaxial cable220.

If the transmitted electromagnetic wave is cut off, however, the receiverate of the electromagnetic wave in the receive antenna 220 a is veryweak. Accordingly, the electromagnetic wave of the weakest receive ratecan be analyzed as the cutoff frequency. The frequency analyzer 400 canidentify the weakest frequency by analyzing a frequency, an amplitude,and so on of the obtained electromagnetic wave. It is therefore possibleto analyze/obtain the cutoff frequency.

Furthermore, if there is electromagnetic wave absorbed by the plasma 100a, the electromagnetic wave is weakly reflected from the transmitantenna 220 a and the first coaxial cable 220. It causes to generateresonance in the sheath space between the plasma 100 a and the transmitantenna 220 a by way of a kind of a cavity, resulting in a strongabsorption of the electromagnetic wave. Therefore, a signal of thereflected electromagnetic wave becomes the weakest. That is, it is meantthat a ratio in which the electromagnetic wave is reflected from thetransmit antenna again is low. It is possible to obtain/acquire acorresponding frequency band of the absorbed electromagnetic wave byanalyzing a frequency band, amplitude, etc. of the weakly reflectedelectromagnetic wave. Accordingly, there is provided a structure capableof analyzing/acquiring an absorption frequency band.

A computer 500 is provided to calculate an electron density and anelectron temperature based on the occurrence of a series of theelectromagnetic waves, a received command, and analyzed frequency data.The computer 500 is electrically connected the electromagnetic wavegenerator 300 and the frequency analyzer 400.

Therefore, if the electromagnetic wave transceiver 200 is connected tothe plasma 100 a within the reaction container 100 and transmitselectromagnetic wave, a frequency band, etc. is obtained from a weaklyreceived electromagnetic wave and data of a cutoff frequency and anabsorption frequency are transmitted to the computer 500. Calculationequations capable of calculating an electron density and/or an electrontemperature based on a frequency are programmed into the computer 500.Accordingly, a structure that can calculate and acquire an electrondensity and electron temperature of a corresponding plasma 100 a can beprovided.

FIG. 3 is a view illustrating convey within the reaction container 100of the electromagnetic wave transceiver 200 shown in FIG. 1.

As shown in FIG. 3, the monitoring apparatus according to the presentinvention includes a conveyer 600. To the other end of theelectromagnetic wave transceiver 200 is connected the conveyer 600.

In the present invention, the conveyer 600 may have a power structurethat allows for a straight-line convey, such as a stepping motorstructure or an oil-pressure cylinder structure. The conveyer 600 isconstructed to convey the electromagnetic wave transceiver 200, which isdisposed to move along a radial direction within the cylindricalreaction container 100, in a straight line forward and backward.

As described above, the conveyer 600 is constructed to convey theelectromagnetic wave transceiver 200 in the straight line. Therefore,the electromagnetic wave transceiver 200 can transmit/receiveelectromagnetic wave while moving in the straight line within the plasma100 a. Furthermore, there is provided a structure capable of analyzing,measuring, and monitoring spatial distributions of an electron densityand electron temperature of a corresponding plasma 100 a.

FIG. 4 a is a graph illustrating cutoff frequencies measured using themonitoring apparatus according to an embodiment of the presentinvention, and FIG. 4 b is a graph illustrating absorption frequenciesmeasured using the monitoring apparatus according to an embodiment ofthe present invention.

Referring to FIG. 4 a, the X axis denotes a frequency band (Hz) and theY axis denotes an amplitude of electromagnetic wave (au.), which isreceived by the receive antenna 220 a. From FIG. 4 a, it can be seenthat as the frequency increases, the amplitude increases, then decreasesat about 1.5×10⁹ Hz, and then becomes the lowest at a frequency of about2.5×10⁹ Hz (indicated by an arrow in the drawing). A portion indicatingthe lowest amplitude, of ones in which the electromagnetic wave receivedas described above is indicated as the frequency band versus theamplitude, is the cutoff frequency.

The cutoff frequency is a frequency of a band that does not transmit theplasma 100 a when the transmit antenna 210 a transmits theelectromagnetic wave to the plasma 100 a as mentioned earlier.Accordingly, a very weak signal is received by the receive antenna 220a. The cutoff frequency serves as an index to detect an electron densityof the plasma 100 a.

In the present embodiment, the electromagnetic wave generator 300generates electromagnetic waves. The generated electromagnetic waves areconsecutively transmitted to the transmit antenna 210 a through thefirst coaxial cable 210 on a frequency basis and are then transmitted tothe plasma 100 a.

The electromagnetic waves that have been transmitted and have been cutoff and weaken in the plasma 100 a as described above are continuouslyreceived by the receive antenna 220 a. The electromagnetic waves arethen transmitted to the frequency analyzer 400 connected to the secondcoaxial cable 220 and are then analyzed on a frequency-band basis.

The analyzed data are transmitted to the computer 500 and are thenindicated as the graph as shown in FIG. 4 a. Furthermore, what isindicated as a frequency band of the lowest amplitude in the graph isthe cutoff frequency. Therefore, there is provided a structure in whichthe computer 500 can calculate/acquire an electron density of acorresponding plasma 100 a based on the cutoff frequency acquiredthrough the above operation.

In addition, referring to FIG. 4 b, an X axis denotes a frequency band(Hz) and a Y axis denotes a predetermined reflection coefficient (dB).Accordingly, in the case where electromagnetic waves are transmitted toa corresponding plasma 100 a, an absorption frequency can be acquired byanalyzing electromagnetic wave of a corresponding frequency having thelowest reflection coefficient through a process in which theelectromagnetic wave is reflected and received.

Analyzed data of the absorption frequency obtained as described aboveare transmitted to the computer 500. Accordingly, there is provided astructure in which the computer 500 can measure an electron temperatureof a corresponding plasma 100 a based on the analyzed data.

FIG. 5 is a graph illustrating electron density and electron temperaturemeasured using the monitoring apparatus according to an embodiment ofthe present invention.

Referring to FIG. 5, an X axis denotes a pressure (mTorr) of the plasma100 a within the reaction container 100, and a Y axis on the right sidedenotes an electron density (cm⁻³) of the plasma 100 a on a pressurebasis and a Y axis on the left side denotes an electron temperature (eV)of the plasma 100 a on a pressure basis.

From FIG. 5, it can be seen that in the case where argon (Ar) plasma isused in the present invention, the electron density of the plasma 100 aincreases as the gas pressure increases, but the electron temperature ofthe plasma 100 a decreases as the discharge gas pressure increases.

Therefore, FIG. 5 shows that the slope of the graph of the electrondensity indicated by a straight line and triangles is opposite to theslope of the graph of the electron temperature indicated by a straightline and squares.

It has been illustrated above that the apparatus for monitoring anelectron density and electron temperature of a plasma according to anembodiment of the present invention has a structure in which oneelectromagnetic wave transceiver 200 in which the conveyer 600 isconnected to one end of the reaction container 100 is mounted. However,the present invention can be applied to a structure in which respectiveelectromagnetic wave transceivers 200 are mounted in the other side, andupper and lower sides of the reaction container 100, and the conveyers600 are connected to the respective electromagnetic wave transceivers200 and measure three-dimensional spatial distributions of an electrondensity and electron temperature of the X-Y-Z axis while moving withinthe reaction container 100 in the respective axial directions.

Furthermore, the transmit antenna 210 a and the receive antenna 220 a ofthe straight-line type have been illustrated above as means fortransmitting and receiving electromagnetic wave. It is however to benoted that a loop antenna, a superturnstile antenna, an excitationantenna, a parabola antenna or the like may be selectively used as themeans for transmitting and receiving electromagnetic wave.

FIG. 6 is a flowchart illustrating a method of measuring an electrontemperature of a plasma according to an embodiment of the presentinvention.

Referring to FIG. 6, a method of monitoring an electron temperatureusing the electron temperature monitoring apparatus of the presentinvention includes a first step (S1) of allowing the electromagneticwave generator 300 to apply electromagnetic wave of a predeterminedfrequency to the transmit antenna 210 a, a second step (S2) of allowingthe receive antenna 220 a to analyze a frequency of the electromagneticwave received from the transmit antenna 210 a, a third step (S3) ofmeasuring a cutoff frequency based on the analyzed frequency, a fourthstep (S4) of calculating an electron density of a plasma using themeasured cutoff frequency, a fifth step (S5) of allowing theelectromagnetic wave generator 300 to transmit electromagnetic wave,monitor reflected wave returned to the transmit antenna 210 a, andmeasure a surface wave absorption frequency, and a sixth step (S6) ofcalculating an electron temperature based on the plasma density and theabsorption frequency found in the fourth step (S4) and the fifth step(S5), respectively.

In the case of a process employing common plasma, the plasma itselfincludes a unique plasma frequency whose state is changed. The plasmafrequency is directly related to the plasma density. Therefore, theelectron density of the plasma can be measured directly by measuring theplasma frequency.

In the event that a frequency of common electromagnetic wave correspondsto the plasma frequency, the frequency has a property that if theelectromagnetic wave is incident on the plasma, it is cut off and doesnot transmit the plasma. Therefore, if the electromagnetic wavegenerating apparatus transmits a frequency of 50 kHz to 10 GHz to thetransmit antenna, the electromagnetic wave output from the transmitantenna can be received by the receive antenna.

At this time, electromagnetic wave having the plasma frequency decidedaccording to the plasma density does not pass through the plasma.Accordingly, the electromagnetic wave is not received by the receiveantenna or only a very weak signal is received by the receive antenna.

That is, as shown in FIG. 4 a, the cutoff frequency of the lowest valuecan be found from the frequency spectrum through the frequency analyzer400. The cutoff frequency is a plasma frequency (ω_(pe)). The electrondensity of the plasma can be found based on the plasma frequency(ω_(pe)) in accordance with the following Equation 1.

μ_(p2) =[n _(e) e ²/ε₀ m _(e)]^(1/2)   [Equation 1]

where ω_(pe) is the plasma frequency, n_(e) is the electron density ofthe plasma, ε₀ is the dielectric constant in the vacuum, and e and m_(e)are the electron charge and mass, respectively.

Meanwhile, if the electromagnetic wave generator 300 transmitselectromagnetic wave and the transmit antenna 210 a monitors returnedreflected wave, a surface wave absorption frequency of the transmitantenna 210 a can be measured.

In other words, the spectrum of the electromagnetic wave reflected fromthe transmit antenna 210 a of FIG. 1 is shown in FIG. 4 b. A dispersionequation of the surface wave can be expressed in the following Equation2.

[1−[ω_(pe)/ω]² ]={K _(m)(βa)I _(m)′(βa)K _(m)(βb)−K _(m)′(βa)I_(m)(βb)}/{K _(m)′(βa)I _(m)′(βa)I _(m)(βa)K _(m)(βb)−K _(m)(βa)I_(m)(βb)}  [Equation 2]

where ω is the absorption frequency, ω_(pe) is the plasma frequency,K_(m), I_(m), K_(m)′, and I_(m)′ are modified Bessel functions, β=2π/λ,λ=2l, and l is the length of the transmit antenna, a is the radius fromthe center of a metal unit of the transmit antenna to the boundary ofthe sheath, and b is the radius of the metal unit of the transmitantenna.

Furthermore, an electron temperature T_(e) can be found using thesurface wave dispersion equation of the above-mentioned Equation 2, aDebye length λ_(d) defined by the following Equation 3, and the width sof the sheath. FIG. 2 shows the relationship between the sheath width sof the transmit antenna, and “a” and “b”.

λ_(d)=(ε₀ T _(w) /n _(e) e ²)^(1/2)   [Equation 3]

s=nλ_(d)

where λ_(d) is the Debye length, T_(e) is the electron temperature ofthe plasma, n_(e) is the electron density of the plasma, ε₀ is thedielectric constant in the vacuum, e is the electron charge, s is thewidth of the sheath wherein s=a−b, and n is a given integer.

Therefore, the cutoff frequency is the plasma frequency ω_(pe) and otherparameters are constants corresponding to a structural antenna size.Accordingly, the electron temperature T_(e) can be found by measuringthe absorption frequency ω.

In accordance with an apparatus and method for monitoring an electrondensity and electron temperature of a plasma according to the presentinvention, an electron density and electron temperature of a plasma canbe measured by detecting an eigenfrequency. Therefore, the presentinvention is advantageous in that it can be applied to a thin filmplasma chemical deposition method of a semiconductor fabricationprocess, a plasma process apparatus in a dry etch process, and so on.

Furthermore, the apparatus of the present invention can be used as aplasma real-time monitoring apparatus. Therefore, there is an advantagein that the apparatus of the present invention can be utilized as areliable process equipment since it can check a current status of aprocess equipment.

While the present invention has been described with reference to theparticular illustrative embodiments, it is not to be restricted by theembodiments but only by the appended claims. It is to be appreciatedthat those skilled in the art can change or modify the embodimentswithout departing from the scope and spirit of the present invention.

1. An apparatus for monitoring an electron density and electrontemperature of a plasma, comprising: an electromagnetic wave generatorthat continuously transmits electromagnetic wave of a series offrequency bands; an electromagnetic wave transceiver connected to aplasma within a reaction container and electrically connected to theelectromagnetic wave generator so that a frequency of the transmittedelectromagnetic wave is correlated to the electron density and electrontemperature of the plasma, the electromagnetic wave transceivertransmitting the electromagnetic wave; a frequency analyzer electricallyconnected to the electromagnetic wave transceiver, for analyzing thefrequency of the electromagnetic wave received from the electromagneticwave transceiver; and a computer electrically connected to theelectromagnetic wave generator and the frequency analyzer, forcalculating a correlation between the electron density and electrontemperature, and a corresponding electromagnetic wave based on afrequency band-based transmission command of the electromagnetic waveand the analyzed data.
 2. The apparatus as claimed in claim 1, whereinthe electromagnetic wave transceiver comprises: first and second coaxialcables that are electrically connected to the electromagnetic wavegenerator and the frequency analyzer, respectively, and are disposed inparallel; and a transmit antenna and a receive antenna that areconnected to and projected from one ends of the first and second coaxialcables, respectively, on the same axial line and are connected to theplasma in order to transmit and receive the electromagnetic wave.
 3. Theapparatus as claimed in claim 2, wherein each of the first and secondcoaxial cables comprises a dielectric-coated layer coated/shielded at apredetermined thickness.
 4. The apparatus as claimed in claim 1, furthercomprising a conveyer connected to the other end of the electromagneticwave transceiver, for causing the electromagnetic wave transceiver to beselectively conveyed within the reaction container.
 5. The apparatus asclaimed in claim 4, wherein the conveyer is driven by a stepping motor.6. The apparatus as claimed in claim 5, wherein the electromagnetic wavetransceiver is disposed along a radial direction of the reactioncontainer.
 7. The apparatus as claimed in claim 6, wherein the conveyeris driven by an oil-pressure cylinder.
 8. The apparatus as claimed inclaim 7, wherein the electromagnetic wave transceiver is disposed alonga radial direction of the reaction container.
 9. A method of monitoringan electron density and electron temperature of a plasma using anapparatus including an electromagnetic wave generator that continuouslytransmits electromagnetic wave of a series of frequency bands; anelectromagnetic wave transceiver connected to a plasma within a reactioncontainer and electrically connected to the electromagnetic wavegenerator so that a frequency of the transmitted electromagnetic wave iscorrelated to the electron density and electron temperature of theplasma, the electromagnetic wave transceiver transmitting theelectromagnetic wave; a frequency analyzer electrically connected to theelectromagnetic wave transceiver, for analyzing the frequency of theelectromagnetic wave received from the electromagnetic wave transceiver;and a computer electrically connected to the electromagnetic wavegenerator and the frequency analyzer, for calculating a correlationbetween the electron density and electron temperature, and acorresponding electromagnetic wave based on a frequency band-basedtransmission command of the electromagnetic wave and the analyzed data,the method comprising: a first step of allowing the electromagnetic wavegenerator to apply electromagnetic wave of a predetermined frequency tothe transmit antenna; a second step of allowing the receive antenna toanalyze a frequency of the electromagnetic wave received from thetransmit antenna; a third step of measuring a cutoff frequency based onthe analyzed frequency; a fourth step of calculating an electron densityof a plasma using the measured cutoff frequency; a fifth step ofallowing the electromagnetic wave generator to transmit electromagneticwave, monitor reflected wave returned to the transmit antenna, andmeasure a surface wave absorption frequency; and a sixth step ofcalculating an electron temperature of the plasma based on the electrondensity of the plasma and the absorption frequency found in the fourthstep and the fifth step, respectively.
 10. The method as claimed inclaim 9, wherein the electron density of the plasma in the fourth stepis found according to the following Equation 1, i.e., a relationalexpression of a plasma frequency ω_(pe) (.i e., the cutoff frequency).ω_(pe) =[n _(e) e ²/ε₀ m _(e)]^(1/2)   [Equation 1] where ω_(pe) is theplasma frequency, n_(e) is the electron density of the plasma, ε₀ is adielectric constant in the vacuum, and e and m_(e) are an electroncharge and mass, respectively.
 11. The method as claimed in claim 9,wherein the electron temperature T_(e) of the plasma in the sixth stepis found according to the following Equation 2 and Equation 3.[1−[ω_(pe)/ω]² ]={K _(m)(βa)I _(m)′(βa)K _(m)(βb)−K _(m)′(βa)I_(m)(βb)}/{K _(m)′(βa)I _(m)(β_(a))K _(m)(βb)−K _(m)(βa)I_(m)(βb)}  [Equation 2] where ω is the absorption frequency, ω_(pe) isthe plasma frequency, K_(m), I_(m), K_(m)′, and I_(m)′ are modifiedBessel functions, β=2π/λ, λ=2l, and l is the length of the transmitantenna, a is a radius from the center of a metal unit of the transmitantenna to the boundary of a sheath, and b is a radius of the metal unitof the transmit antenna.λ_(d)=(ε₀ T _(e) /n _(e) e ²)^(1/2)   [Equation 3]s=nλ_(d) where λ_(d) is a Debye length, T_(e) is the electrontemperature, n_(e) is the electron density of the plasma, ε₀ is thedielectric constant in the vacuum, e is the electron charge, s is thewidth of the sheath wherein s=a−b, and n is a given integer.